This posture is known as Buddha Dispelling Mara. 'Mara' means evil, or fear. It is the grounding gesture of touching the earth that dispels Mara, allowing Buddha to focus on meditation, detaching himself from the emotional response of fear to the disturbance of Mara.

Buddhism on the Web

An excellent online source for buddhist texts, both online and
through their CD-ROM, the Internet
Sacred Text Archive CD-ROM 3.0. Includes Mahayana, Therevada,
Tibetan and Zen texts, along with ancillary materials, not to
forget thousands of documents from the world's many religions,
philosophies and arts.

This is a quiet place in cyberspace devoted to religious tolerance
and scholarship

Theists, agnostics and atheists are all welcome within Buddhism
(and in this group); Buddhists make up their own minds about the
existence or nonexistence of deities, if they get around to it.
Some people find this question uninteresting, feeling that neither
a 'yes' nor a 'no' answer contributes meaningfully to the elimination
of suffering.

There are two major streams of Buddhism. The earliest Theravada
(meaning "Doctrine of the elders"), is based on texts (sutras)
written in the Pali language very close to that spoken by Buddha.
This site, an excellent Theravada resource, includes translations
of the Pali canon and a good history
of Theravada. An excerpt of that history:

Owing to its historical dominance in southern Asia (Sri Lanka,
Thailand, and Burma), Theravada is also identified as "Southern
Buddhism," in contrast to "Northern Buddhism," which migrated
northwards from India into China, Tibet, Japan, and Korea. Theravada
is often equated with "Hinayana" (the "Lesser Vehicle"), in contrast
to "Mahayana" (the "Greater Vehicle"), which is usually a synonym
for Zen, Ch'an, and other expressions of Northern Buddhism. The
use of "Hinayana" as a pejorative has its origins in the early
schisms within the monastic community that ultimately led to the
emergence of what would later become Mahayana. Today scholars
of many persuasions use the term "Hinayana" without pejorative
intent...

The Mahayanists ... did not see themselves as creating a new start
for Buddhism, rather they claimed to be recovering the original
teachings of Buddha, in much the same way that the Protestant
reformers of sixteenth century Europe claimed that they were not
creating a new Christianity but recovering the original form.
The Mahayanists claimed that their canon of scriptures represented
the final teachings of Buddha; they accounted for the non-presence
of these teachings in over five hundred years by claiming that
these were secret teachings entrusted only to the most faithful
followers.

I have a personal preference for the more light-hearted Mahayana
forms over Theravadan asceticism. Whichever is the 'truer' form
of Buddhism, I prefer the inflection that the filter of Chinese
Daoism placed on the path which is best
summed up by a Tendai proverb: To a Tendai monk, everything
is wonderful. That is, in The
Vinegar Tasters, Saicho would be smiling alongside Laozi.
The following is excerpted from Tendai
for Americans, reproduced in full on the site.

According to the Tendai view, all men, without exception, possess
in their innermost being, the Buddha-nature, and are, therefore,
capable of attaining to Nirvana. There are none who are doomed,
except by themselves. All that is required is sincere practice.

Just to give you an idea what monastic life is like. Source
from Gerald Roscoe's The
Monastic Life.

Two hours before the sun appears on the eastern horizon the
pealing of the temple bell signals the time, 4 a.m. In the kuti
the monks, having spent the night on a thin mattress under a plain
cotton blanket, open their eyes and rise from sleep to start the
day. The Buddha said that four hours sleep should be enough for
a monk, but nowadays monks generally sleep at least six hours,
and when the bell wakes them, there is no hesitation about rising.

Recommended Buddhism Reading

This book and the next, both from the Theravadan branch of Thailand,
were my introduction to Buddhism. They contain essentially the
same information though this one appears to be the more well-known.
From a review:

One of the first things to be said about this book is that it
is eminently readable. It should make a powerful appeal to two
kinds of persons. First, those largely ignorant of Buddhism who
are sincerely eager to repair that ignorance will find it exactly
what they need. Second, a good many people with a fairly extensive
knowledge of Buddhism would be happy to have it on their bookshelves
because it provides a complete summary of all the essentials of
Buddhist teachings and practice.

Excerpts and explorations of this book appear within my article
Vipassana
Climber. Now, just to show that authors of these two books
are of the same mind, Roscoe paraphrases Mills:

Dukkha should not be translated [simply] as suffering because
there is plenty of experience in the world which is pleasant but,
like all conditioned things, is impermanent, and therefore even
though it is not suffering it is dukkha.

This beautiful book documents in image and text a peculiar yet
exhileratingly unique group of monks. The Tendai monks of Mount
Hiei in Kyoto include among their buddhist practices running marathons.
But to a Tendai monk, "marathon" means running approximately
26 miles every day for a year. In hand-made straw sandals (several
pairs a day).

In 1995, the Nomadic Spirit had the pleasure of visiting the monks of
Mt. Hiei's Shugakuin temple. There are photographs
and an Nomadic Spirit entry on this site.